An actuated magnetic field is generated at a plurality of distinct frequencies that at least partially cancels an outside magnetic field at the plurality of distinct frequencies, thereby yielding a total residual magnetic field. The total residual magnetic field is coarsely detected and a plurality of coarse error signals are respectively output. The total residual magnetic field is finely detected and a plurality of fine error signals are respectively output. The actuated magnetic field is controlled respectively at the plurality of distinct frequencies at least partially based on at least one of the plurality of coarse error signals, and finely controlled respectively at the plurality of distinct frequencies at least partially based on at least one of the plurality of fine error signals.

A method includes applying, to a sample exhibiting optical scattering and having a emission particles distributed therein that exhibit spin-dependent fluorescence, a magnetic field to shift a resonance frequency of each emission particle in a position-dependent manner. The method also includes exciting the sample with an excitation beam that causes at least one emission particle to emit spin-dependent fluorescence and detecting the emitted spin-dependent fluorescence. The method also includes estimating a position of the emission particle(s) within the sample based on the spin-dependent fluorescence, the resonance frequency, and the magnetic field. The method also includes estimating optical transmission information for the sample based on a wavefront of the excitation beam and the estimated position. The optical transmission information including a measure of an optical field at each position of an emission particle.

The invention concerns a method for the hyperpolarisation of .sup.13C nuclear spin in a diamond, comprising an optical pumping step, in which colour centre electron spins in the diamond are optically pumped. The method further comprises a transfer step in which the polarisation of a long-lived state of the colour centre electron spins is transferred to .sup.13C nuclear spins in the diamond via a long-range interaction.

A time-multiplexed dual atomic magnetometer includes first and second vapor cells such that an external magnetic field induces Larmor precession of atoms within the vapor cells. The magnetometer includes first and second polarimeters for measuring first and second polarizations of first and second probe beams that propagate through the first and second vapor cells, respectively. The magnetometer includes a controller that gates the probe beams such that (i) the first probe beam propagates through the first vapor cell during a first measurement stage, (ii) the second probe beam does not propagate through the second vapor cell during the first measurement stage, (iii) the second probe beam propagates through the second vapor cell during a second measurement stage that begins when the first measurement stage ends, and (iv) the first probe beam does not propagate through the first vapor cell during the second measurement stage.

A light-trapping geometry enhances the sensitivity of strain, temperature, and/or electromagnetic field measurements using nitrogen vacancies in bulk diamond, which have exterior dimensions on the order of millimeters. In an example light-trapping geometry, a laser beam enters the bulk diamond, which may be at room temperature, through a facet or notch. The beam propagates along a path inside the bulk diamond that includes many total internal reflections off the diamond's surfaces. The NVs inside the bulk diamonds absorb the beam as it propagates. Photodetectors measure the transmitted beam or fluorescence emitted by the NVs. The resulting transmission or emission spectrum represents the NVs' quantum mechanical states, which in turn vary with temperature, magnetic field strength, electric field strength, strain/pressure, etc.

Disclosed is a method of generating atomic spin orientation in an atomic ensemble. The method includes providing a steady magnetic field (5) to the atomic ensemble to cause a Zeeman splitting within first and second manifolds of the ground state of the atomic energy levels of the atomic ensemble. The method includes pumping the atomic ensemble with an electromagnetic optical radiation beam, the beam being detuned from a transition involving the first manifold such that a majority of the atomic population of the first manifold in the atomic ensemble is transferred from the first manifold into a magnetic Zeeman sublevel of the second manifold. A system for generating an atomic spin orientation in a 15 atomic ensemble is also disclosed.

An atomic magnetometer system is disclosed that includes a variable magnetic field source (14) configured to provide an oscillating primary magnetic field to cause a sample (16) to produce a secondary magnetic field. The atomic magnetometer system also includes an atomic magnetometer for detecting the secondary magnetic field. The atomic magnetometer includes an atomic specimen, a pump and probe subsystem configured to pump the atomic specimen to create a polarisation and to probe atomic coherence precession within the atomic specimen with a probe beam, a detector configured to detect the probe beam to produce a detection signal. The system is configured to drive the variable magnetic field source (14) in dependence on the detection signal with a frequency tuned to rf resonance. A method of operating an atomic magnetometer is also disclosed.

An apparatus useful for creating and measuring states of an entangled system, comprising a pair of interacting multi-level systems, each of systems comprising a state |g>, a state |r>, and state |r*>. One or more first electromagnetic fields excite a first transition between the ground state |g> and the state |r> to create an entangled system. One or more second electromagnetic fields are tuned between the state |r> and the intermediate state |r*> so that any population of the systems in |r*> are dark to a subsequent detection of a population in the systems in |g>, providing a means to distinguish the entangled system in the state |g> and the entangled system in the state |r>. In one or more examples, the systems comprise neutral Rydberg atoms.

A magnetic field gradiometer for determining a magnetic field gradient includes at least one excitation light source for emitting excitation light, and two spatially spaced-apart measuring areas for magnetic field measurement. Color centers in diamond are arranged in the two measuring areas. The color centers emit fluorescent light upon excitation using the excitation light. The magnetic field gradiometer further includes at least one microwave emitter for applying at least one microwave field to the spatially spaced-apart measuring areas, two detectors for detecting the fluorescent light from the two spatially spaced-apart measuring areas, and an evaluator for determining the magnetic field gradient based on the fluorescent light detected by the two detectors. The two measuring areas are configured as freestanding measuring waveguides of a common diamond crystal. The diamond crystal is used as a substrate for the measuring waveguides.

A physical state measurement apparatus includes a main solid material which generates fluorescence by excitation light from a light source part. A microwave application part applies microwaves to the main solid material so as to control an electron state of the main solid material. A detection part detects the physical state of an object to be measured by the fluorescence from the main solid material. A feedback part has a solid material for feedback and a control part and detects a difference in amplitude between operating points on a low-frequency side and a high-frequency side of a lowering portion of a spectrum amplitude centered on a resonance frequency of an electron spin resonance spectrum of fluorescence from the solid material for feedback and feedback-controls the microwave application part such that the difference becomes zero.